This invention relates to magnetic transducers, and more particularly, to write heads for use in disc drives and methods for fabricating such write heads.
Disc drive write heads for perpendicular recording typically include a soft ferromagnetic yoke that is wrapped around a coil of one or more turns. An electrical current in a coil, produces a magnetic field that aligns the yoke magnetization along the field direction. For perpendicular writing, a soft underlayer is typically employed in the magnetic recording media such that the write field extends between the pole tip and soft underlayer. When the write field exceeds the coercivity and demagnetization field of the media, a domain forms with its magnetization aligned along the write field direction. These domains form the bits of digital data that can be detected by a read head.
The objective of increasing magnetic storage areal densities requires extremely narrow track-widths in the recording media. The narrowing of the track width will necessarily reduce the cross-sectional area of the writer pole tip. This will increase the yoke reluctance and, consequently, decrease the writer efficiency. A drop in efficiency will require a larger write current. However, the write current cannot be made arbitrarily large without producing undesirable levels of Joule heating. Furthermore, it is difficult and expensive to produce large-amplitude current pulses with fast rise times. In addition, the use of high-moment materials in the writer requires larger write currents to switch the magnetization, in comparison to heads made with softer, lower moment alloys.
The effective write field of a head is related to head geometry and the saturation magnetization (4xcfx80Ms) of the pole material. In the perpendicular head geometry, the write field utilizes the deep gap field to xe2x80x9cwritexe2x80x9d as opposed to the fringing field utilized in longitudinal head geometries. Perpendicular transducers typically include a top pole and a bottom pole, with the top pole having a smaller cross-sectional area than the bottom pole at an air bearing surface. A single material is usually used for the top pole. This top pole material must exhibit a large saturation magnetization (4xcfx80Ms), low coercivity, and a well-defined uniaxial anisotropy. The largest known saturation magnetization at room temperature is exhibited by Fe65Co35 which has a value of xcx9c2.4T. However, FeCo has not been used as a perpendicular top pole. One characteristic that prevents the use of FeCo in top poles is that the material is not uniaxial, therefore, it has nearly zero permeability which would result in an inefficient write head. In addition to magnetics, high moment materials such as FeCo, which are sputtered, have to be etched in order to define the track width. For areal densities of 100 Gbit/in2 and greater, track widths are less than 100 nm. For these small track widths, a process such as reactive ion etching (RIE) is typically used, however, FeCo has no known volatile reaction products at practical processing temperatures and cannot be etched via RIE.
In summary, a perpendicular write head having a top pole including a high magnetic saturation material is desirable, however, the inherent magnetics and the need to form narrow track widths have prevented the use of materials such as FeCo in top poles.
There is a need for a magnetic write head that can achieve increased areal data densities in magnetic recording media.
A write head for a disc drive constructed in accordance with this invention comprises a yoke including a top pole and a bottom pole, the top pole including a layer of insulating material, a layer of a first magnetic material positioned on a surface of the layer of insulating material, the first magnetic material having a first end positioned adjacent to an air bearing surface of the write pole, and a layer of a second magnetic material positioned on the surface of the layer of insulating material, the second magnetic material having a lower magnetic moment than the first magnetic material and being positioned to conduct magnetic flux between the return pole and the layer of first magnetic material.
The invention also encompasses a method of fabricating write heads including: providing a yoke including a top pole and a bottom pole, the top pole including a layer of insulating material, depositing a layer of a first magnetic material on a surface of the layer of insulating material, the first magnetic material having a first end positioned adjacent to an air bearing surface of the write pole, and depositing a layer of a second magnetic material on the surface of the layer of insulating material, the second magnetic material having a lower magnetic moment than the first magnetic material and being positioned to conduct magnetic flux between a return pole and the layer of first magnetic material.
The invention further encompasses a disc drive including a motor for rotating at least one magnetic storage medium, a write head for producing areas of magnetization on the magnetic storage medium, an arm for supporting the write head, an actuator for pivoting the arm to position the write head, and the write head including a yoke including a top pole and a bottom pole, the top pole including a layer of insulating material, a layer of a first magnetic material positioned on a surface of the layer of insulating material, the first magnetic material having a first end positioned adjacent to an air bearing surface of the write pole, and a layer of a second magnetic material positioned on the surface of the layer of insulating material, the second magnetic material having a lower magnetic moment than the first magnetic material and being positioned to conduct magnetic flux between the return pole and the layer of first magnetic material.